The present invention relates to a pressure fluid control valve device in which pressure fluid such as exhaust gas exhausted from an internal combustion engine is flowed into two paths selectively or simultaneously.
Such device is disclosed in U.S. patent application Ser. No. 08/258499 entitled "Valve Device for Controlling a High Temperature Fluid", in which there is provided a valve device for controlling a high temperature fluid, comprising a main passage for the fluid; a secondary passage for the fluid disposed in parallel with the main passage; a first valve disc provided in the main passage and perpendicular to the main passage; a second valve disc provided in the secondary passage and perpendicular to the secondary passage; a first valve shaft for rotating the first valve disc; a second valve shaft for rotating the second valve disc disposed in the same axis as that of the first valve shaft; and a shaft coupling for connecting the end of one of the first and second valve shafts with the end of the other valve shaft with a gap for allowing thermal expansion of the valve shafts. There is advantage that the first valve shaft for opening and closing the valve disc for the first passage and the second valve shaft for opening and closing the valve disc for the second passage are provided respectively, and by connecting the first and second valve shafts by the shaft coupling with the gap, axial thermal expansion of the first and second valve shafts is allowable. Even if one of the valve shafts is thermally expanded, the other will not be affected by the expansion, thereby preventing unsmooth operation of opening and closing.
As example of such coupling, a jack shaft coupling comprises a recess at the end of one of valve shafts adjacent to each other; and a projection at the end of the other of the valve shafts, whereby the valve shafts are axially movable, but is not rotatable to each other. In the foregoing valve device, the coupling has diameter larger than that of the valve shaft, or the outer circumferential surface of the jack shaft coupling has a notch, the corner of which rubs the bearing surface to increase wear of the bearing surface. Thus, it is not preferable to bear the coupling portion directly, but the coupling portion is provided far from a bearing portion of each valve shaft. As a result, in a partition wall between the paths, there are provided two bearings for two valve shafts adjacent to each other with a length required to receive the coupling, thereby increasing the width of the partition wall and the length of the valve shafts to make the device itself larger, which is disadvantageous.